Posterior-stabilized rotating-platform (PSRP) knee was designed with the purpose of improving postoperative flexion and stability. Its long-term performance has limited reports, which could show whether this purpose has been realized without deleterious effect. We report its long-term results at 10-13 years, of a previously studied cohort, evaluated longitudinally.
A total of 133 consecutive PSRP implants, selected for 118 patients were studied. Twenty-one patients (24 knees) were deceased and 11 patients (12 knees) were lost to follow-up after 10 years. Eighty patients (97 knees) completed clinical evaluation, of whom 78 patients (88 knees) also completed radiological evaluation.
Mean flexion improved from 106.8° (30°-150°) to 127° (90°-155°). Forty-three percent patients could sit crosslegged, 32.5% could sit on floor, and 3.4% could squat. Mean knee subscore of Knee Society Score improved from 28 (1-59) to 96 (67-100). Mean function subscore improved from 53 (5-81) to 78 (−10 to 100). After 10 years, 5 patients had zero function score because of developing other debilitating medical illnesses. Twenty-one dead patients (24 knees), at their last follow-up (7.7 years), had satisfactory scores. No patient had spinout or revision. Radiologically, alignment was satisfactory and there was no osteolysis. Kaplan-Meier analysis showed 100% implant survival.
PSRP design, evaluated after 10 years of implantation in selected patients, had 100% survival with good flexion. Addition of post and cam to the original rotating platform design has provided good stability without untoward effects of wear or osteolysis at 10-13 years.